This invention relates to drive mechanisms for powering the drive wheels of vehicles. More particularly, it provides a unique drive mechanism for powering a vehicle, utilizing a prime mover driven at a substantially constant speed at which efficiency of performance is optimized.
With the energy crisis confronting the world, it is imperative to produce vehicles which are as efficient and consume as little fuel and emit as few combustion by-products as possible. The traditional internal combustion engine as heretofore used in drive mechanisms for vehicles is notoriously inefficient, particularly because it is typically operated over a wide range of speeds within which the efficiency of performance varies considerably. The present invention utilizes a prime mover which is driven at a substantially constant speed, so that the efficiency of power development may be optimized and emissions minimized. Provision is made to vary the operating speed of the primer mover depending upon the range of desired vehicle speeds. For example, the prime mover may be operated at a first, relatively low speed for city driving of an automobile, e.g., for speeds less than about 30 to 40 miles per hour. The prime mover may be operated at another, higher speed, for vehicle operation in the country, e.g., speeds in excess of 40 miles per hour. For any given operation, the prime mover speed is maintained constant to optimize the efficiency of power development and to minimize emissions.
The prime mover drives an hydraulic pump which in turn drives an hydraulic motor. The output flow of the pump is controlled to determine vehicle speed and direction. A bypass fluid circuit is utilized to permit free wheeling of the vehicle in the forward direction of movement, in particular. It is believed preferable to provide no free wheeling capability in the reverse direction of vehicle movement. In this fashion, the drive system of the vehicle may be used as an emergency braking means, so that if the brake system of the vehicle fails, the drive system may be placed in the "reverse" mode to prevent free wheeling and to provide natural braking of the vehicle.
While constant speed prime movers have been used in the past, and while hydraulic pump and motor combinations have also been utilized, it is not believed that a drive system for an automobile, utilizing a constant speed prime mover driving an hydraulic pump which in turn drives an hydraulic motor has been utilized in the past to provide vehicle movement over the whole range of permissible vehicle speeds, e.g., zero to 80 and more miles per hour.
The following patents and publication are representative of the prior art:
______________________________________ U.S. Patent No. Date Patentee ______________________________________ 2,431,719 Dec. 2, 1947 G. W. Wilkin 3,352,373 Nov. 14, 1967 R. M. Tuck 3,509,721 May 5, 1970 J. M. Crawford 3,587,765 June 28, 1971 J. W. McFarland 3,612,202 Oct. 12, 1971 H. C. Moon, Jr. et al 3,637,036 Jan. 25, 1972 G. W. Swisher, Jr. et al 3,817,341 June 18, 1974 C. K. Greene 3,892,283 July 1, 1975 J. W. Johnson ______________________________________ Publication: Engineering Application Manual, Bulletin 9565, Rev. E., January, 1975. Published by Sundstrand Hydro-Transmission, Ames, Iowa, a unit of Sundstrand Corporation